Sciencemadness Discussion Board

Synthesis of Chloroacetic acid

Kloberth - 30-1-2024 at 00:40

My plan would be to use AcOH as solvent for Sodium acetate and a bit of Iodine as catalyst when bubbling in chlorine gas. Also a incondescent light beside the reaction flask. would this work fine?

bnull - 30-1-2024 at 06:00

I would suggest sulfur in place of iodine. Or you can try both and see which one is better.

unionised - 30-1-2024 at 06:08

It will probably work - at least a bit.
The interesting question is what plans do you have for trapping the chlorine if it doesn't?

Kloberth - 30-1-2024 at 08:07

well iodine doesnt work you just get finest tar in the end. i have tried in the past sulfur and it worked to an extend (about 25% yield) which waveleght of light do you need for this reaction exactly, couldbt find any information on that.

Kloberth - 30-1-2024 at 08:08

and also the sodium acetate is useless in my opinion just a hassle trying to destill everything out of the reactiob flask when there is so much salt.

clearly_not_atara - 30-1-2024 at 08:45

You shouldn't need any light with a sulfur catalyst, in this case the mechanism is fully ionic and not radical.

First S2Cl2 reacts with acetic acid to give acetic anhydride and HCl.

Then the HCl enolizes some of the acetone anhydride.

Then the enol reacts with Cl2 to acetic-chloroacetic anhydride.

Then this transesterifies with another molecule of acetic acid to regenerate acetic anhydride and release chloroacetic acid.

The difficulty is in making sure that the acetic acid is dry to start with, since water poisons the reaction.

bnull - 30-1-2024 at 13:08

Quote: Originally posted by Kloberth  
well iodine doesnt work you just get finest tar in the end.

Also, there is a chance of some iodoacetic acid being formed all along. Nasty stuff, toxic as hell. (Although an excess chlorine would transform it into chloracetic acid... and an iodine chloride or something worse.)

Quote: Originally posted by clearly_not_atara  
The difficulty is in making sure that the acetic acid is dry to start with, since water poisons the reaction.

Addition of acetic anhydride solves the problem. If he has acetic anhydride, of course.

I'm curious. Why did you use sodium acetate?

Kloberth - 30-1-2024 at 15:29

i tried it because i saw a comment suggesting using iodine as the catalyst and acetic anhydride to remove the hcl gas and drive the reaction forward.

was just curious if it worked.